Change UIPageViewController page programmatically

Question

I am using UIPageViewController having Next button that have same functionality like swipe to next view.

@IBAction func next(sender: UIButton!) {

    let pageContentViewController = pageViewController.viewControllers![0] as! WelcomeViewController
    let index = pageContentViewController.pageIndex + 1

    if index < titleArray.count {
        let vctoMove = self.viewControllerAtIndex(index) as WelcomeViewController
        let viewControllers = NSArray(objects: vctoMove)
        pageViewController.setViewControllers(viewControllers as? [UIViewController], direction: .Forward, animated: true, completion: nil)
    }
}